Uterine Cancer
Cancer of the corpus uteri (endometrial cancer) is the sixth most common cancer in women. Globally, it is diagnosed with an incidence rate of 8.2 in 100,000, representing 4.8% of all cancer cases in women. In 2012, 320,000 women were diagnosed with endometrial cancer. The mortality rate of 1.8 in 100,000 women is substantially lower than the incidence rate. Regarding cancer of the cervix uteri, which is the fourth most common cancer in women, there were 528,000 cases diagnosed in 2012, corresponding to an incidence rate of 14 in 100,000 women or 7.9% of all cancers diagnosed in women. Again, with 6.8 per 100,000 the mortality rate of cervix uteri cancer is clearly lower than the incidence rate (World Cancer Report, 2014).
Incidence rates of endometrial cancer vary greatly between countries; close to two thirds of the estimated new cases occur in countries with very high or high levels of human development. Accordingly, incidence rates are elevated in northern and eastern Europe and North America (age-standardized rate (ASR)=14 and 19 per 100,000, respectively), and tend to be low in North Africa and West Asia (ASR=5 per 100,000) (World Cancer Report, 2014).
Cervical cancer affects predominantly women in lower-resource countries; almost 70% of the global burden occurs in areas with low or medium levels of human development, and more than one fifth of all new cases of cervical cancer are diagnosed in India. The disease is the most common cancer among women in 39 of the 184 countries worldwide, and is the leading cause of cancer death in women in 45 countries. These countries are mainly in sub-Saharan Africa (ASR=35 per 100,000), parts of Asia, and some countries in Central and South America (ASR=21 per 100,000). The lowest incidence rates tend to be in western Europe (ASR=11 per 100,000), North America, Australia and New Zealand, and the eastern Mediterranean (World Cancer Report, 2014).
The 1-year survival rate for endometrial cancer is about 92% while it is about 87% for cervical cancer (SEER Stat facts, 2014). The 5-year survival rate for endometrial cancer is 82% and 68% for cervical cancer. As for many cancers, endometrial cancer is an age-related disease. The probability of dying from endometrial cancer is <0.1% before 50 years of age, 0.2% between 50 and 70 years and 0.5% for women above 70 years. In contrast, the lifetime risk of dying from cervical cancer is bimodal, peaking in the group of woman below 50 years as well as above 70 years (American Cancer Society, 2015).
More than 80% of endometrial cancers occur as endometrioid adenocarcinomas (type I), a form that is associated with estrogen exposure and that is well to moderately differentiated. Obesity is among the risk factors for endometrioid cancer, being estimated to account for up to 40% of cases worldwide (World Cancer Report, 2014). Further risk factors are high blood pressure and diabetes mellitus (National Cancer Institute, 2015). Progestogen-containing oral contraceptives decrease the risk. Principal genetic lesions include microsatellite instability and mutations of the PTEN, PIK3CA, ARID1A, KRAS, and CTNNB1 (β-catenin) genes (World Cancer Report, 2014).
Besides endometrioid adenocarcinomas there are non-estrogen-related high-grade endometrial carcinomas (nonendometrioid serous and clear cell adenocarcinomas, type II) that are associated with poor prognosis. Non-endometrioid carcinomas are associated with TP53 and PPP2R1A mutations, loss of E-cadherin, HER2/neu amplification, and loss of heterozygosity at multiple loci (World Cancer Report, 2014).
Cervical cancer presents in two main histological types: squamous cell carcinoma (85-90%) and adenocarcinoma (10-15%), which are equally strongly associated with human papillomavirus (HPV) infection, a major risk factor for cervical cancer. HPV causes precancerous lesions that may be detected and treated. The mean age of developing low grade lesions is 24-27 years and 35-42 years for high grade-lesions. At least 20% of high-grade lesions progress to invasive carcinoma within 10 years. HPV vaccination offers a preventive option. The most common somatic mutations in cervical cancer were found for PIK3CA, and are associated with shorter survival (World Cancer Report, 2014).
Treatment of endometrial carcinomas is stage-dependent. The majority of endometrical carcinomas comprises of well to moderately differentiated endometrioid adenocarcinomas which are usually confined to the corpus uteri at diagnosis and can be cured by hysterectomy (World Cancer Report, 2014). Alternatively, to maintain fertility in patients with early stage endometrical carcinomas and the desire to have children, a conservative therapy with Megesterolacetat may be an option. However the high relapse rate needs to be considered. For patients with progressed endometrical carcinomas, a hysterectomy preceding other palliative approaches may improve life quality as well as prognosis. It is frequently combined with adjuvant radiotherapy. Inoperable patients receive primary radiotherapy. If neither excision nor radiation are possible, progesterone-receptor-positive carcinomas are treated with gestagene or tamoxifen. In case of progression upon endocrine therapy or progesterone-receptor-negative carcinomas, patients receive Adriamycin, Cisplatin, Carboplatin, Paclitaxel, or Docetaxel (Leitlinie Endometriumkarzinom, 2008). Furthermore, Megestrol Acetate has been FDA approved for the palliative treatment of advanced endometrial cancer (National Cancer Institute, 2015). Patients carrying a PTEN mutation are treated with PARP-inhibitors (Dedes et al., 2010).
Also therapies for cervical cancer depend on the stage. In early stages, excision is the standard therapy which might be combined with radio-(chemo-) therapy. Primary radio-(chemo-) therapy is chosen at late stages (Stage III and higher), in cases with lymph node infiltration or in cases in which the tumor cannot be excised. The localization of radiation is adapted according to lymph node infiltration and radiation is supported by Cisplatin (S3-Leitlinie Zervixkarzinom, 2014). It has been shown that combined radio-(chemo-) therapy with Cisplatin is beneficial in terms of overall survival (OS) and progression free survival (PFS) as compared to radiotherapy alone. Of note, combinations with other medications did not improve OS or PFS as compared to cisplatin alone but increased toxicity (Green et al., 2005; Wang et al., 2011; Lukka et al., 2002). In the treatment of local relapses, combinations of Cisplatin with other drugs have been tested and only a combination with Topotecan resulted in improved OS as compared to Cisplatin alone (S3-Leitlinie Zervixkarzinom, 2014).
There are also some immunotherapeutic approaches that are currently being tested. In a Phase I/II Clinical Trial patients suffering from uterine cancer were vaccinated with autologous dendritic cells (DCs) electroporated with Wilms' tumor gene 1 (WT1) mRNA. Besides one case of local allergic reaction to the adjuvant, no adverse side effects were observed and 3 out of 6 patients showed an immunological response (Coosemans et al., 2013).
As stated above, HPV infections provoke lesions that may ultimately lead to cervical cancer. Therefore, the HPV viral oncoproteins E6 and E7 that are constitutively expressed in high-grade lesions and cancer and are required for the onset and maintenance of the malignant phenotype are considered promising targets for immunotherapeutic approaches (Hung et al., 2008; Vici et al., 2014). One study performed Adoptive T-cell therapy (ACT) in patients with metastatic cervical cancer. Patients receive an infusion with E6 and E7 reactive tumor-infiltrating T cells (TILs) resulting in complete regression in 2 and a partial response in 1 out of 9 patients (Stevanovic et al., 2015). Furthermore, an intracellular antibody targeting E7 was reported to block tumor growth in mice (Accardi et al., 2014). Also peptide, DNA and DC-based vaccines targeting HPV E6 and E7 are in clinical trials (Vici et al., 2014).
Considering the severe side-effects and expense associated with treating cancer, there is a need to identify factors that can be used in the treatment of cancer in general and uterine cancer in particular. There is also a need to identify factors representing biomarkers for cancer in general and uterine cancer in particular, leading to better diagnosis of cancer, assessment of prognosis, and prediction of treatment success.
Immunotherapy of cancer represents an option of specific targeting of cancer cells while minimizing side effects. Cancer immunotherapy makes use of the existence of tumor associated antigens.
The current classification of tumor associated antigens (TAAs) comprises the following major groups:
a) Cancer-testis antigens: The first TAAs ever identified that can be recognized by T cells belong to this class, which was originally called cancer-testis (CT) antigens because of the expression of its members in histologically different human tumors and, among normal tissues, only in spermatocytes/spermatogonia of testis and, occasionally, in placenta. Since the cells of testis do not express class I and II HLA molecules, these antigens cannot be recognized by T cells in normal tissues and can therefore be considered as immunologically tumor-specific. Well-known examples for CT antigens are the MAGE family members and NY-ESO-1.b) Differentiation antigens: These TAAs are shared between tumors and the normal tissue from which the tumor arose. Most of the known differentiation antigens are found in melanomas and normal melanocytes. Many of these melanocyte lineage-related proteins are involved in biosynthesis of melanin and are therefore not tumor specific but nevertheless are widely used for cancer immunotherapy. Examples include, but are not limited to, tyrosinase and Melan-A/MART-1 for melanoma or PSA for prostate cancer.c) Over-expressed TAAs: Genes encoding widely expressed TAAs have been detected in histologically different types of tumors as well as in many normal tissues, generally with lower expression levels. It is possible that many of the epitopes processed and potentially presented by normal tissues are below the threshold level for T-cell recognition, while their over-expression in tumor cells can trigger an anticancer response by breaking previously established tolerance. Prominent examples for this class of TAAs are Her-2/neu, survivin, telomerase, or WT1.d) Tumor-specific antigens: These unique TAAs arise from mutations of normal genes (such as β-catenin, CDK4, etc.). Some of these molecular changes are associated with neoplastic transformation and/or progression. Tumor-specific antigens are generally able to induce strong immune responses without bearing the risk for autoimmune reactions against normal tissues. On the other hand, these TAAs are in most cases only relevant to the exact tumor on which they were identified and are usually not shared between many individual tumors. Tumor-specificity (or -association) of a peptide may also arise if the peptide originates from a tumor- (-associated) exon in case of proteins with tumor-specific (-associated) isoforms.e) TAAs arising from abnormal post-translational modifications: Such TAAs may arise from proteins which are neither specific nor overexpressed in tumors but nevertheless become tumor associated by posttranslational processes primarily active in tumors. Examples for this class arise from altered glycosylation patterns leading to novel epitopes in tumors as for MUC1 or events like protein splicing during degradation which may or may not be tumor specific.f) Oncoviral proteins: These TAAs are viral proteins that may play a critical role in the oncogenic process and, because they are foreign (not of human origin), they can evoke a T-cell response. Examples of such proteins are the human papilloma type 16 virus proteins, E6 and E7, which are expressed in cervical carcinoma.
T-cell based immunotherapy targets peptide epitopes derived from tumor-associated or tumor-specific proteins, which are presented by molecules of the major histocompatibility complex (MHC). The antigens that are recognized by the tumor specific T lymphocytes, that is, the epitopes thereof, can be molecules derived from all protein classes, such as enzymes, receptors, transcription factors, etc. which are expressed and, as compared to unaltered cells of the same origin, usually up-regulated in cells of the respective tumor.
There are two classes of MHC-molecules, MHC class I and MHC class II. MHC class I molecules are composed of an alpha heavy chain and beta-2-microglobulin, MHC class II molecules of an alpha and a beta chain. Their three-dimensional conformation results in a binding groove, which is used for non-covalent interaction with peptides.
MHC class I molecules can be found on most nucleated cells. They present peptides that result from proteolytic cleavage of predominantly endogenous proteins, defective ribosomal products (DRIPs) and larger peptides. However, peptides derived from endosomal compartments or exogenous sources are also frequently found on MHC class I molecules. This non-classical way of class I presentation is referred to as cross-presentation in the literature (Brossart and Bevan, 1997; Rock et al., 1990). MHC class II molecules can be found predominantly on professional antigen presenting cells (APCs), and primarily present peptides of exogenous or transmembrane proteins that are taken up by APCs e.g. during endocytosis, and are subsequently processed.
Complexes of peptide and MHC class I are recognized by CD8-positive T cells bearing the appropriate T-cell receptor (TCR), whereas complexes of peptide and MHC class II molecules are recognized by CD4-positive-helper-T cells bearing the appropriate TCR. It is well known that the TCR, the peptide and the MHC are thereby present in a stoichiometric amount of 1:1:1.
CD4-positive helper T cells play an important role in inducing and sustaining effective responses by CD8-positive cytotoxic T cells. The identification of CD4-positive T-cell epitopes derived from tumor associated antigens (TAA) is of great importance for the development of pharmaceutical products for triggering anti-tumor immune responses (Gnjatic et al., 2003). At the tumor site, T helper cells, support a cytotoxic T cell− (CTL−) friendly cytokine milieu (Mortara et al., 2006) and attract effector cells, e.g. CTLs, natural killer (NK) cells, macrophages, and granulocytes (Hwang et al., 2007).
In the absence of inflammation, expression of MHC class II molecules is mainly restricted to cells of the immune system, especially professional antigen-presenting cells (APC), e.g., monocytes, monocyte-derived cells, macrophages, dendritic cells. In cancer patients, cells of the tumor have been found to express MHC class II molecules (Dengjel et al., 2006).
Elongated (longer) peptides of the invention can act as MHC class II active epitopes. T-helper cells, activated by MHC class II epitopes, play an important role in orchestrating the effector function of CTLs in anti-tumor immunity. T-helper cell epitopes that trigger a T-helper cell response of the TH1 type support effector functions of CD8-positive killer T cells, which include cytotoxic functions directed against tumor cells displaying tumor-associated peptide/MHC complexes on their cell surfaces. In this way tumor-associated T-helper cell peptide epitopes, alone or in combination with other tumor-associated peptides, can serve as active pharmaceutical ingredients of vaccine compositions that stimulate anti-tumor immune responses.
It was shown in mammalian animal models, e.g., mice, that even in the absence of CD8-positive T lymphocytes, CD4-positive T cells are sufficient for inhibiting manifestation of tumors via inhibition of angiogenesis by secretion of interferon-gamma (IFNγ) (Beatty and Paterson, 2001; Mumberg et al., 1999). There is evidence for CD4 T cells as direct anti-tumor effectors (Braumuller et al., 2013; Tran et al., 2014).
Since the constitutive expression of HLA class II molecules is usually limited to immune cells, the possibility of isolating class II peptides directly from primary tumors was previously not considered possible. However, Dengjel et al. were successful in identifying a number of MHC Class II epitopes directly from tumors (WO 2007/028574, EP 1 760 088 B1).
Since both types of response, CD8 and CD4 dependent, contribute jointly and synergistically to the anti-tumor effect, the identification and characterization of tumor-associated antigens recognized by either CD8+ T cells (ligand: MHC class I molecule+peptide epitope) or by CD4-positive T-helper cells (ligand: MHC class II molecule+peptide epitope) is important in the development of tumor vaccines.
For an MHC class I peptide to trigger (elicit) a cellular immune response, it also must bind to an MHC-molecule. This process is dependent on the allele of the MHC-molecule and specific polymorphisms of the amino acid sequence of the peptide. MHC-class-1-binding peptides are usually 8-12 amino acid residues in length and usually contain two conserved residues (“anchors”) in their sequence that interact with the corresponding binding groove of the MHC-molecule. In this way each MHC allele has a “binding motif” determining which peptides can bind specifically to the binding groove.
In the MHC class I dependent immune reaction, peptides not only have to be able to bind to certain MHC class I molecules expressed by tumor cells, they subsequently also have to be recognized by T cells bearing specific T cell receptors (TCR).
For proteins to be recognized by T-lymphocytes as tumor-specific or -associated antigens, and to be used in a therapy, particular prerequisites must be fulfilled. The antigen should be expressed mainly by tumor cells and not, or in comparably small amounts, by normal healthy tissues. In a preferred embodiment, the peptide should be over-presented by tumor cells as compared to normal healthy tissues. It is furthermore desirable that the respective antigen is not only present in a type of tumor, but also in high concentrations (i.e. copy numbers of the respective peptide per cell). Tumor-specific and tumor-associated antigens are often derived from proteins directly involved in transformation of a normal cell to a tumor cell due to their function, e.g. in cell cycle control or suppression of apoptosis. Additionally, downstream targets of the proteins directly causative for a transformation may be up-regulated and thus may be indirectly tumor-associated. Such indirect tumor-associated antigens may also be targets of a vaccination approach (Singh-Jasuja et al., 2004). It is essential that epitopes are present in the amino acid sequence of the antigen, in order to ensure that such a peptide (“immunogenic peptide”), being derived from a tumor associated antigen, and leads to an in vitro or in vivo T-cell-response.
Basically, any peptide able to bind an MHC molecule may function as a T-cell epitope. A prerequisite for the induction of an in vitro or in vivo T-cell-response is the presence of a T cell having a corresponding TCR and the absence of immunological tolerance for this particular epitope.
Therefore, TAAs are a starting point for the development of a T cell based therapy including but not limited to tumor vaccines. The methods for identifying and characterizing the TAAs are usually based on the use of T-cells that can be isolated from patients or healthy subjects, or they are based on the generation of differential transcription profiles or differential peptide expression patterns between tumors and normal tissues. However, the identification of genes over-expressed in tumor tissues or human tumor cell lines, or selectively expressed in such tissues or cell lines, does not provide precise information as to the use of the antigens being transcribed from these genes in an immune therapy. This is because only an individual subpopulation of epitopes of these antigens are suitable for such an application since a T cell with a corresponding TCR has to be present and the immunological tolerance for this particular epitope needs to be absent or minimal. In a very preferred embodiment of the invention it is therefore important to select only those over- or selectively presented peptides against which a functional and/or a proliferating T cell can be found. Such a functional T cell is defined as a T cell, which upon stimulation with a specific antigen can be clonally expanded and is able to execute effector functions (“effector T cell”).
In case of targeting peptide-MHC by specific TCRs (e.g. soluble TCRs) and antibodies or other binding molecules (scaffolds) according to the invention, the immunogenicity of the underlying peptides is secondary. In these cases, the presentation is the determining factor.